SH2 Domain-Containing Inositol Polyphosphate 5′-Phosphatase Is the Main Mediator of the Inhibitory Action of the Mast Cell Function-Associated Antigen1
SH2 Domain-Containing Inositol Polyphosphate 5′-Phosphatase Is the Main Mediator of the Inhibitory Action of the Mast Cell Function-Associated Antigen1
复制标题
含有SH2结构域的肌醇多磷酸5′-磷酸酶是肥大细胞功能相关抗原1抑制作用的主要介质
作者：
Rong Xu;J. Abramson;M. Fridkin;I. Pecht
肥大细胞功能相关抗原(MAFA)是一种II型膜糖蛋白，最初发现于大鼠粘膜型肥大细胞(RBL-2H3系)的质膜上。MAFA的胞外区和胞内区分别含有C型凝集素结构域和免疫受体酪氨酸抑制基序(ITIM)。此前已有研究表明，MafA聚集性抑制了这些细胞对FcεRI刺激的分泌反应。在这里，我们显示了ITIM的酪氨酸经历了磷酸化，在MAFA聚集，这是显著增强的过钒酸盐处理细胞。此外，蛋白酪氨酸激酶Lyn的Src同源3结构域直接与含有非磷酸化MAFA ITIM和PAAP基序的多肽结合。体外和体内实验结果表明，Lyn可能是这种ITIM磷酸化的原因，这种磷酸化增加了Lyn对多肽的Src同源结构域2(SH2)的亲和力。体外实验表明，酪氨酸磷酸化的MAFA ITIM多肽还与肌醇5‘-磷酸酶(SHIP)的SH2结构域以及蛋白酪氨酸磷酸酶-2结合。然而，前一个领域的强度是后一个领域的8倍。进一步支持SHIP在MAFA作用中的作用源于体内实验，在这些实验中发现酪氨酸磷酸化的MAFA主要与SHIP结合。在过度表达野生型SHIP的RBL-2H3细胞中，MAFA聚集性对分泌反应的抑制明显强于表达正常SHIP水平的对照细胞或过度表达野生型蛋白酪氨酸磷酸酶-2或其主要负型的细胞。相反，在SH2结构域的过表达时，MAFA的抑制作用基本上被取消。综上所述，这些结果表明SHIP是介导MAFA抑制RBL-2H3细胞对FcεRI刺激反应的主要酶。
The mast cell function-associated Ag (MAFA) is a type II membrane glycoprotein originally found on the plasma membrane of rat mucosal-type mast cells (RBL-2H3 line). A C-type lectin domain and an immunoreceptor tyrosine-based inhibitory motif (ITIM) are located in the extracellular and intracellular domains of MAFA, respectively. MAFA clustering has previously been shown to suppress the secretory response of these cells to the FcεRI stimulus. Here we show that the tyrosine of the ITIM undergoes phosphorylation, on MAFA clustering, that is markedly enhanced on pervanadate treatment of the cells. Furthermore, the Src homology 3 domain of the protein tyrosine kinase Lyn binds directly to a peptide containing nonphosphorylated MAFA ITIM and PAAP motif. Results of both in vitro and in vivo experiments suggest that Lyn is probably responsible for this ITIM phosphorylation, which increases the Src homology domain 2 (SH2) affinity of Lyn for the peptide. In vitro measurements established that tyrosine-phosphorylated MAFA ITIM peptides also bind the SH2 domains of inositol 5′-phosphatase (SHIP) as well as protein tyrosine phosphatase-2. However, the former single domain is bound 8-fold stronger than both of the latter. Further support for the role of SHIP in the action of MAFA stems from in vivo experiments in which tyrosine-phosphorylated MAFA was found to bind primarily SHIP. In RBL-2H3 cells overexpressing wild-type SHIP, MAFA clustering causes markedly stronger inhibition of the secretory response than in control cells expressing normal SHIP levels or cells overexpressing either wild-type protein tyrosine phosphatase-2 or its dominant negative form. In contrast, on overexpression of the SH2 domain of SHIP, the inhibitory action of MAFA is essentially abolished. Taken together, these results suggest that SHIP is the primary enzyme responsible for mediating the inhibition by MAFA of RBL-2H3 cell response to the FcεRI stimulus.
DOI：
10.1073/pnas.93.4.1689
发表时间：
1996-02-20
影响因子：
11.1
作者：
Damen, JE;Liu, L;Krystal, G
通讯作者：
Krystal, G
影响因子：
10.5
作者：
L. Rohrschneider;J. Fuller;I. Wolf;Yan Liu;D. Lucas
通讯作者：
L. Rohrschneider;J. Fuller;I. Wolf;Yan Liu;D. Lucas
利用磷酸酪氨酸抗血清鉴定 v-src、v-yes、v-fps、v-ros 和 v-erb-B 致癌酪氨酸蛋白激酶的多种新型多肽底物。
影响因子：
8
作者：
Kamps,MP;Sefton,BM
通讯作者：
Sefton,BM